Fuel cell system

Abstract

There is provided a fuel cell system capable of minimizing the formation of a local cell even if the start and the stop are repeated, thereby substantially reducing a degradation in performance of the fuel cell. The fuel cell system includes a fuel cell; a hydrogen supply unit for supplying hydrogen to an anode channel of the fuel cell; an air-amount adjusting unit for adjusting the amount of air supplied to a cathode channel of the fuel cell and discharged from the cathode channel; an external load connected to the fuel cell; and a control unit for controlling an operation of the hydrogen supply unit, the air-amount adjusting unit, and the external load; in which the control unit controls the fuel cell system such that the cathode channel of the fuel cell is filled with air whose pressure is not higher than a saturated vapor pressure at the time of starting the fuel cell system, thereafter, the air is continuously led through the cathode channel of the fuel cell, and a load is drawn from the fuel cell.

1 . A fuel cell system comprising:
 a fuel cell;   a hydrogen supply unit for supplying hydrogen to an anode channel of the fuel cell;   an air-amount adjusting unit for adjusting the amount of air supplied to a cathode channel of the fuel cell and discharged from the cathode channel;   an external load connected to the fuel cell; and   a control unit for controlling an operation of the hydrogen supply unit, the air-amount adjusting unit and the external load,   wherein the control unit controls the fuel cell system such that the cathode channel of the fuel cell is filled with air whose pressure is not higher than a saturated vapor pressure at the time of starting the fuel cell system, thereafter, the air is continuously led through the cathode channel of the fuel cell, and a load is drawn from the fuel cell.   
     
     
         2 . The fuel cell system according to  claim 1 ,
 wherein the air-amount adjusting unit includes an air supply line for supplying air to the cathode channel of the fuel cell, a cathode pressure regulation valve and an air pressure sensor provided on the air supply line, an air discharge line for discharging air from the cathode channel of the fuel cell, and an air outlet valve provided on the air discharge line, and   the control unit controls the fuel cell system such that the cathode channel of the fuel cell is filled with air whose pressure is not higher than the saturated vapor pressure through the air supply line with the air outlet valve closed to make a pressure in the cathode channel higher than a pressure in the cathode channel at the time of power generation.   
     
     
         3 . The fuel cell system according to  claim 2 ,
 wherein the control unit controls the fuel cell system such that the air outlet valve is opened to discharge at a burst the air with which the cathode channel is filled when the cathode channel of the fuel cell is filled with air whose pressure is not higher than the saturated vapor pressure through the air supply line to continuously lead the air through the cathode channel.   
     
     
         4 . The fuel cell system according to  claim 3 ,
 wherein a load is drawn from the fuel cell after the air is led through the cathode channel, thereby the maximum value of an output voltage per unit fuel cell is set to 800 mV or less.   
     
     
         5 . The fuel cell system according to  claim 2 , further comprising a voltage sensor for measuring the output voltage of the fuel cell,
 wherein the amount of air supplied to the cathode channel is controlled based on an information from the air pressure sensor and the voltage sensor which are attached to the fuel cell when the cathode channel is filled with air whose pressure is not higher than the saturated vapor pressure.   
     
     
         6 . The fuel cell system according to  claim 5 ,
 wherein the supply of air is stopped and an output voltage per unit fuel cell is reduced if the output voltage is higher than a first predetermined threshold voltage after the supply of air is started with the air outlet valve closed; on the other hand, the supply of air is stopped and the air outlet valve is opened to lower the output voltage if the output voltage is not higher than the first threshold voltage and the output voltage is higher than a second predetermined threshold voltage after the pressure of air with which the cathode channel is filled is increased, when the cathode channel is filled with air whose pressure is not higher than the saturated vapor pressure.